Comparing the Topological and Electrical Structure of the North American Electric Power Infrastructure

The topological (graph) structure of complex networks often provides valuable information about the performance and vulnerability of the network. However, there are multiple ways to represent a given network as a graph. Electric power transmission and distribution networks have a topological structure that is straightforward to represent and analyze as a graph. However, simple graph models neglect the comprehensive connections between components that result from Ohm's and Kirchhoff's laws. This paper describes the structure of the three North American electric power interconnections, from the perspective of both topological and electrical connectivity. We compare the simple topology of these networks with that of random (Erdos and Renyi, 1959), preferential-attachment (Barabasi and Albert, 1999) and small-world (Watts and Strogatz, 1998) networks of equivalent sizes and find that power grids differ substantially from these abstract models in degree distribution, clustering, diameter and assortativity, and thus conclude that these topological forms may be misleading as models of power systems. To study the electrical connectivity of power systems, we propose a new method for representing electrical structure using electrical distances rather than geographic connections. Comparisons of these two representations of the North American power networks reveal notable differences between the electrical and topological structure of electric power networks

CAN EXISTING MULTI-PURPOSE HYDROELECTRIC ASSETS SMOOTH UTILITY-SCALE WIND VARIABILITY?

The integration of large-scale wind energy in the United States will require controllable assets to provide more supplemental energy to maintain electrical reliability. Previous work has identified hydropower as an advantageous asset, due to its flexibility and low emissions production. While many dams currently provide energy and environmental services in the United States and globally, we find that multi-use hydropower facilities would face policy conflicts if asked to store and release water to accommodate wind integration. Specifically, we develop a model simulating hydroelectric operational decisions along a multi-use river system when the electric facility is able to provide wind integration services through a mechanism that we term ‘flex reserves’. We use Kerr Dam in North Carolina as a case study, simulating operations under two alternative reservoir policies, one reflecting current policies and the other regulating flow levels to promote downstream ecosystem conservation. Even under perfect information, Kerr Dam faces policy conflicts in providing any substantial levels of ‘flex reserves ’ while maintaining release levels consistent with other river management goals. These policy conflicts are exacerbated during periods of low flow. Increasing payments for provision of flex reserves does not solve the policy conflict. 1

Improvement of Shelf Life for Space Food Through a Hurdle Approach

The processed and prepackaged spaceflight food system is a critical human support system for manned space flights. As missions extend longer and farther from Earth over the next 20 years, strategies to stabilize the nutritional and sensory quality of food must be identified. For a mission to Mars, the space foods themselves must maintain quality for up to 5 years to align with cargo prepositioning scenarios. Optimizing the food system to achieve a 5-year shelf life mitigates the risk of an inadequate food system during extended missions. Because previous attempts to determine a singular pathway to a 5-year shelf life for food were unsuccessful, this investigation combines several approaches, based on science, technological advancement, and past empirical evidence, that will define the prepackaged food system for long duration missions. This study supports the Advanced Food Technology strategic planning process by identifying food processing, packaging, and storage technologies that will be required for exploration missions and the extent that they must be implemented to achieve a 5-year shelf life for the entire food system

Should Natural Gas Be Shipped or Stored to Supply Power Plants?

Following a series of winters featuring extreme cold episodes in the Northeastern U.S., power grid operators have engaged in exercises focused on assessing fuel deliverability to power plants, particularly natural gas. These studies have raised important issues and identified possible scenarios that could contribute to reliability problems during winter peaks, but have not evaluated the economics of specific solutions to winter-time fuel deliverability. This paper describes an expansion to a new modeling framework for gas and electric power transmission planning problems (the Combined Electricity and Gas Expansion, or CEGE model) that allows centralized or distributed natural gas storage to be evaluated alongside traditional planning alternatives such as transmission network expansion. Using a test system based on the gas and electric transmission topology in New England, we develop a a simple two-period gas storage model and use this model to evaluate economically valuable locations for distributed natural gas storage and compare the economic merits of increasing storage within New England versus expanding pipeline infrastructure to increase fuel deliverability to New England power plants within our test system. Initial simulations using this storage model suggest that the optimal placement for gas storage may be co-located with power plants to relieve binding pressure constraints in areas of the gas network close to gas-fired generation. Moreover, the economic consequences of extreme winter peak scenarios may be ameliorated at a lower cost with a mix of gas storage and pipeline expansions rather than via pipeline expansion alone

Internet Protocol version 6 and the future of home networking

Home networking will be more of a necessity in the future than it is today. The homes of the future will make our lives easier in many ways. As microprocessors become less expensive and require less power they will be implanted into many of the common household items used everyday. Appliances and components will evolve into smart devices that communicate with each other. Connecting these devices will become more important as devices incorporate new technologies. It will be necessary to build a network that can handle the needs of this type of computing environment. The home networks of the future will require many of the same features that can be found in today\u27s corporate networks. However, there will be four issues that will determine the level of success of implementing home networks. The first issue is the increase in volume of the devices accessing and utilizing the Internet. Security will be a high priority for homeowners, since the data that accumulates and circulates in and out of the home is sensitive and personal. The third critical issue is ease of use, because the average homeowner does not have the skills necessary to configure and maintain networks. The last issue that will be important in the home is the increased need for bandwidth and the ability to accommodate all types of data traffic. There is no doubt that the Internet Protocol will be important in future home networks. Some proponents of IP say IP over everything The trend has been finding new ways of making IP the answer to all types of voice and data communications. Initially the Internet Protocol was designed for a specific application. Over time, IPv4 has been able to successfully adapt to the changing needs and demands of the Internet. At one point in the early 90\u27s, it was feared that IPv4 would not be able to meet the future needs. As a result, The Internet Engineering Task Force (IETF) developed a next generation Internet Protocol, referred to as Internet Protocol version 6. In the meantime, new fixes to old IPv4 problems have been temporarily halted. The implementation of IPv6 has been extremely slow since the imminent danger of declining address space has been temporarily addressed. IP version 6 has many new features built into the protocol that will streamline and enhance many aspects of the network, but these features alone may not be enough to cause the displacement of the massive infrastructure of IPv4. Will IPv6 be better at handling the demands of the home networks of the future, or will the additions and updates for IPv4 be sufficient? What are some of the resolutions that are being developed or are already implemented for the key issues in home networks- the increasing number of devices, security, ease of use and data flow

Valuing Technological Flexibility in Low Carbon Electricity Portfolios

With the increased focus on responding to climate change by accelerating a transition to a low carbon energy system, differing views remain on the combination of energy technologies that will best achieve this goal. Identifying technological pathways is complicated by wide uncertainties in economic and technological factors. Analyses that neglect these uncertainties can produce pathways for a low carbon energy future that are highly granular and specific, but which are based on a particular assumption about future conditions and imply a need to make specific technology commitments over a long period of time. We frame the energy transition problem as the identification of one near-term investment strategy that is flexible across a wide range of possible future costs, followed by many alternative subsequent investment plans, each of which responds to realized future costs to achieve an aggressive emissions reduction target. Using an example of planning a low carbon power system under uncertainty, we demonstrate the option value of not ruling out some energy technologies in the near-term

Extension of Space Food Shelf Life Through Hurdle Approach

The processed and prepackaged space food system is the main source of crew nutrition, and hence central to astronaut health and performance. Unfortunately, space food quality and nutrition degrade to unacceptable levels in two to three years with current food stabilization technologies. Future exploration missions will require a food system that remains safe, acceptable and nutritious through five years of storage within vehicle resource constraints. The potential of stabilization technologies (alternative storage temperatures, processing, formulation, ingredient source, packaging, and preparation procedures), when combined in hurdle approach, to mitigate quality and nutritional degradation is being assessed. Sixteen representative foods from the International Space Station food system were chosen for production and analysis and will be evaluated initially and at one, three, and five years with potential for analysis at seven years if necessary. Analysis includes changes in color, texture, nutrition, sensory quality, and rehydration ratio when applicable. The food samples will be stored at -20 C, 4 C, and 21 C. Select food samples will also be evaluated at -80 C to determine the impacts of ultra-cold storage after one and five years. Packaging film barrier properties and mechanical integrity will be assessed before and after processing and storage. At the study conclusion, if tested hurdles are adequate, formulation, processing, and storage combinations will be uniquely identified for processed food matrices to achieve a five-year shelf life. This study will provide one of the most comprehensive investigations of long duration food stability ever completed, and the achievement of extended food system stability will have profound impacts to health and performance for spaceflight crews and for relief efforts and military applications on Earth